Weeding along the creekline at Gloria Park on Sun 21 Nov, we found some Turkey Rhubarb or Rambling Dock, Acetosa sagittata. It has these large potato-like tubers under the ground, all of which you have to find and dig up in order to eradicate it!
Turkey Rhubarb growing near creek, Gloria Park, Hazelbrook. Photo © O. Evans 
Turkey Rhubarb tubers. Photo © O. Evans
Read more in-depth information about identifying and removing this weed on the Weeds of the Blue Mountains website: Turkey Rhubarb